Fluid heating and vaporizing apparatus



Sept. 10, 1929. R. A. CARLETON, 2 5

FLUID HEATING AND VAFORIZING APPARATUS Filed Aug. 23, 1927 3Sheets-Sheet 2 lnvenl'qr. 77 Rober'r A.Curle1'on Sept. 10, 1929.

R. A. CARLETON FLUID HEATING AND VAPORIZING APPARATUS Filed g- 1927 3Sheets-Sheet 3 Robefl A. CurleTon 1W ATTDRPJELIS:

Patented Sept. 1 0, 1929.

i -ourra ;n 'srajrs s Parana" @FFECE;

mROBERT; A; CARLETON,

This invention relates to ii'nprovements'in fluid-heatingfipparatus,"iiif 'whiclilfthe fluid is'l eatetl o'ne more tu'b'ula'r hea'tingeleinentsl forming a, icoiidu ilt. 6r conduits for the fluid and havingwalls oflifelatively high resistance through ;.which an electric currentpassed, saidelectriccurrent' being of prefer ably low voltage asap:'suflicient amperage to raise the heatingfelment to desired degree oftemp'ra tu reil This inventionielates to cer tai'nimprovements in jinypriorf'ap IicatiQmf Seri al No. 214,972; file d th'e twenty-thirdfday ofAugust, 1927." 1 1 p f T Purp ef he: r tn ni t Pm an apparatus. suitablefor heating and e'v'aporating or concentrating liquids, such as sugar,alcohol, brine, acids ind the like, or for va porizingliquidsorgenerating-steam;1 One of the objects of the-invention is"provide a ;rugged-apparatus of simple and economical construction yvhichwilln'ot be subject to chemical action of the fluids being treated andwhich can be readily built in units of any desired size or capacity. I Afurther object of the invention is to provide a fluid heating apparatuscomprismg a tubular heating element having a wall of relatively highresistanceand a. tubular low-resistance conductor for anelectric currentenclosingsaid heating element, electrically connected thereto and soarranged as to transmit the electric currentin theoppo-site direction tothat in which it-passesthrough 1 the heating element, .wherebytheeffects of self-induction will be substantially neutrallzed. i I 1 i-":

A further object of the invention is-t0 pro vide a fluid-heatingapparatus comprising a tubular fluid-containingconductor for theelectric current enclosing a tubular heating element with means forpassing an electric current through said conductorand heating element inopposite directions, whereby the iivrb'fssstmc' Ann varonizmeAPLEARAITUSA for NEWTON CENTER, MASSACHUSETTS.

Application- "theafini ust 23, 1921. "Serial No. 214,973.

effects of self-induction will be'neutralized and heat will betransmitted to t-he'fluid from both the inner and outer surfa ces of thewall of the heating element. 1 A-furtherobject of the invention is topro vide an apparatus of the character described, in which theparticular fluid-containing conductor encloses a plurality of tubularheating elements which are arranged in axial par allelism therewith,with means for causing a current of electricity to flow through the tu-'bular, low-resistance conductor and the tubular heating elem'entsenclosed therein in 0pposite directions, whereby the effects ofselfinduction will be neutralized and the" fluid caused to circulate indirect contact with the inner and outer walls of the heating element.'Affurthe'r'objcct'of the invention is to'provide an apparatus of the'character described in which the electric current supplied to theheating elements is thermostatically c0n trolled by the maximumtemperature of the fluid or its vapors, whereby a substantially uniformheatingof the fluid or itsvapors will be maintained.

A further object of the invention isto supply an apparatus of thecharacter specified with means operable by the flow of the fluidadmitted into theapparatus to complete the electrical circuit throughthe heating elements and upon cessation of said flow to break thecircuit, so that over-heating of the heating elements will be avoided.

Theseand other featuresof the invention will more fully appear from thefollowing description and accompanying claims, and will be particularlypointed out in the claims. Preferred forms of apparatus embodying theinvention are illustrated 'in the accompanying drawings, in which Figure1 is a vertical sectional view of an electric heating apparatusparticularly designed for vaporizing liquids;

Fig. 2 is a transverse horizontal section on line 22, Fig. 1, viewedfrom the top 3 port a spider Fig. 3 is a transverse sectional view online 33, Fig. 1, viewed from the bottom;

Fig. 4 is a vertical sectional view of an em bodiment of the inventionparticularly designed for the evaporization of liquids or the generationof steam;

Fig. 5 is a vertical sectional view on line 55, Fig. 4 of the apparatusshown in that figure;

Fig. 6 is a detail sectional view on line 6-6, Fig. 4, .vierged ,fromthe left;

Fig.,"7 detriil 'sectional view on line 77, Fig. 4;

Fig. 8 is a longitudinal sectional view of one form of tubular-heatingelement embodyingrthe invention; I

ig. 9 is a longitudinal sectional view of a simple form of heatingapparatus embodying the invention; and

Fig. lQ is a transverse sectional view on line 10%10:,F ig.:9, v

Theapparatusillustrated inFigs. 1 to 3 of the"drawing s, which, as abovestated, is particularly designedffdr heating or evaporating andconcentnating liquids, comprises a cylindrical receptacle 1 having, awall of steelror other materialsuitable for nsc with the liquid being.heated and/the pressure required in its treatment and provided withheads 2'and [The receptacleis'(provided with an inlet 4 through; may beintroduced into the receptacle. s

:The lowferi head. desirably is provided with a'blow-ofi 5fandtheu'pperhead 3 with an outlet 6 through, which the. vapors .may bedischargedj l; Brackets. 7., which may be cast, weldedorlotherwise'secured tothe inside of the cylindricaliw allofthereccptaclel, suping central pr vided..witli a central opening 10amaicounter-sunk wall 11 whichfservesas a-seat for a cylindrical Shaving av downwardly-extendconductor 12 of low resistance material.

I Supports ;13 of insulatinglmaterial supporting the cylindricalconductor 12 are seated'upon the spider,.'a nd. similar insulatingsupports 14 restupon the arm s of the spider 8 in proximity to theends'thereof. An outer tubular or cylindrical conductor 15 of lowresistance matcrial rests upon and is electrically connected tothe arms8 ofthe spider.

A metallic grid 16 which rests upon the insulating supports '13 andl tis provided with a series of socket-s17 to receive and support the lowerends of a plurality of preferably circularseries of tubular heatingelements 18, the rid being provided with apertures 19 there etweentopermit circulation of the fluid through the grid. The upper ends of thetubular. heating elements are mounted ina similar grid 20 which issupported by insulating supports 21 and which are supported upona'series of brackets 22.

The tubular heating elements are open at both ends and communicate attheir lower ends with the chamber 23 of the receptacle and at theirupper ends with a chamber 2.4 which forms a vapor space and with whichthe outlet 6 communicates.

The tubular heating elements have relatively thin walls of metal ofrelatively high electric resistance, such as Monel metal, one of themany chrome steel alloys, or other material having suitable resistanceto corrosion by the liquid being treated.

Any suitable means may be provided for supplying an electric current tothe heating element. In the preferred embodiment of the inventionillustrated herein an alternating current is supplied through suitableconductors 25, 26 and a manually-operable switch 27 to the primary28 ofa step-down transformer.

One of the terminals of the secondary 29 of said transformer isconnected, by a suitable conductor 30 which passes through an insulatingbushing 31 in the head 2 of the receptacle, to the grid 16. The otherterminal of the primary of the transformer is connected, by a suitableconductor 32 which passes through an insulating bushing 33 in the head2, to the spider 8, which in turnis electrically connected to thelow-resistance tubular members 12 and 15.

By reason of this construction, a circuit for the electric current iscompleted froni'the primary of the transformer, through the conductor30, the tubular elements 18, the uppergrid 20, the tubularlow-resistance conductors 12 and 15, the spider 8, and conductor 32-;and the current flowing through thecircuit is thus caused to passthrough the tubular heating elements 18 in the opposite direction fromthat in which it passes through the low-resistance conductors 12 and 15.I Thusthe effects of self-induction are greatly diminished orsubstantially neutralized.

Preferably thermostatic nieanssubject to the maximum temperature of thefluid or the vapors therefrom are employed to control the current whichis supplied to the heating elements, so that a substantally constanttern perature may be maintained in the receptacle.

In the construction shown, a thermostat 34 extends into the fluid in thechamber above the upper end of the heating elements. When thetemperature of the fluid exceeds a predetermined degree, the thermostat,which may be of usual type, operates to complete an electric circuitthrough the conductors 35 and 3G and the solenoid or magnetic coil 37 ofa voltage regulator 38 so constructed as to cut in a predeterminednumber of the coils of the primary of the transformer, therebyreducingthe current supplied to the heating elements.

Any other form of controlling mechanism may, of course, be employed.

The receptacle 1 may be provided with a water gua provided paratus.

In the operation of the device, the heatdelivered by the heatingelements to the fluid causes the fluid to flow upwardly through'andbetween the heating elements and to pass downwardly between the tubularlow-resistance conductor and the wall of the receptacle 1, and also.downwardly through the tubularlowwesistance conductor 12, therebyproviding a.continuous circulation. .The fluid thus circulating isheated by die 39 and other usual equipment or heating and evaporatingaprect'co'ntact. with'both the innerand outer surfaces of the walls ofthe heating elements whichi by reason of theircomparatively largeheating-surface area, are enabled to operate at a ver highterminalefliciency, and as the wallsof theheating elements may be madecomparatively thin in cross-section because of the balance of internaland ei'ctern'al pressure, the heat generated is transferred to theliquid at a high rate of speed. i

Furthermore, the walls of the heating elements remain practically at thesame temperature, or ut slightlvhotter than the temperature ofthe-liquid, thus preventing overheating or decomposition of the liquid,or the formation of .scale or undersirable gases.

The'vapor formed from the liquid passes into the vapor's pac'e in theupper portion of the receptacle, and therefrom through the outlet 6' inthe upper head 3. i

In usual evaporating apparatus, steam is employed, inwh'ichthe'temperature available for heating is limited to steam temperature,which, at ,atmospheric-pressure, 'is but 212. If higher temperaturesaredesired, steam, under pressure heated tubularwalls must be ofconsiderable thickness to obtain the requisite strength. The thermalefliciency of such arrangements is low as compared with thatof thepresent invention, becauseof the'low 'coeflicient of heat transfer from.the steam through-the walls of thetube to the liquid being heated, thepresence of scale or deposits on the surface of the tubes and entrainedgas and air, and water or condensate, all of which conditions combine tomake the operation slow, and require that the evaporator be arrangedwith a comparatively large area of heating surface in order to obtainthe required heating effect. I

In the electrically-heated evaporator'herein described, not only is theheating surface practically doubled, because of the arrangement whichallows both the inner andouter surfaces to be used for transmitting heatto the liquid, but any desired temperature can be obtained b regulatingthe flow of current through the lieating. elements, and the temperaturecan be controlled and maintained at any predetermined degree of heatFurthermore, the apparatus can be operatinust'be used, and the v ed toproduce a high degree of lieat at atmospheric pressure, making itpossible to construct apparatus of this type in largercapacities and atlower cost than has here tofore been possible. In Figs. 4, 5, 6 and 7, amodified form of the invention is illustrated which is designed forheating water or other -liquids,-' butsmore particularly for vaporizingliquids.

This apparatus comprises a preferably horizontal tank-4O of steel orother suitable metal provided with heads 41 and 42,- one of which hasa'manhole 43,for cleaning and otherpurposes, a vapor or a steam dr'um44,a pressure regulator 45,- a gauge-glass; ora water column46, andotherusual boiler eq'uip' ment, with conduits 47, 48 extending from thebottom thereof and communicating with afluid-hea'ter.", 4 Thefluid-heater comprises a cylindrical tank-49 0f steel or ;other materialsuited to the liquid being heated and the pressure employed, preferablyarranged'in an inclined position beneath thetank and having at its endsconduits 50 and 51 communicating with the conduits 47 and 48,respectively, with gaskets 52 and 53 of insulating materialtherebetween.

The wall of the cylindrical tank' 49 desirably is formed in twoaxially-aligned sections 54 and '55 of metal having 'relatively lowresistance, and provided at their remote ends, respectively, with heads56 and 57 and at their adjacent ends withoutwardlv-e'xtending annularflanges 158v and 59, which are separated by a gasket 60 of insulatingmaterial and 3 connected together 'by insulating bolts to fo'rmfawater-tight joint; I a

Header plates 61 and 62 of lowresistance material extend transversely ofthe tank 49 1 1n proximity'to the endsjthereof and are welded orotherwise electrically connected to the inner walls of the sections'54'and 55 of the tank-.- a

5 Tubular heating elements 63 composed of a metal of comparatively highelectrical re- 'sistance, such as Monel met-a1, one of the many chromenicked steel alloys, or other material having suitable resistance tocorrosion by the liquid being heated, are mounted at their ends in theheader plates 61 and 62. The tubular heating elements 63 are open attheir ends and communicate, respectively, with the spaces between thegrids 61 and 62 and the heads 56 and 57 of the heater, so that acireulation of the fluid will be caused through the heating elements,the conduits'51 and 48, the tank 40 and the conduits 47and 50 when heatis transmitted to the fluid from the heating elements. In order toprovide for the circulationof the fluid through the intermediate portionof the tank 49, so that the fluid may be heated by direct contact withthe exterior surfaces of the walls of the heating elements and externaland internal pressure upon the walls of the heating elements equalized,the header 61 is provided, preferably along its lower portion, with aplurality of apertures 64, and the header plate 62 is also provided,preferably alon its upper portions, with like apertures 65. v a

,Any suitable means may-be provided for supplying an electricheatingcurrent to the heating elements. In thepreferredconstruction,illustratedherein, the Walls 54: and 55 of thetank 49, whicl i are of metal having low electrical resistance,-are usedas conductors. The flanges 58 and 59 of these sections are oflowresistancemetal and areprovided with suitable terminals or, lugs66.an d 67;through ,which current is supplied from a suitable f ',=ZI;"4' The electric circuit therefore comprises the flang and 9, the-weof t s c n 54 and 55 of the tanlg, the headers-61 and 62 and the highresistance, tubulargheatin elements 63. Preferably :the current issuppied' to the terminals 66 .and G'Ziromthesecondary of a transformer 68,the-primar 69 of. which is supplied through service wires 70 and 71 froma suitable alternating currentgeneraton.

Desirable means are employed for regulating; the current tomaintain asubstantially uniform rate of evaporation of the fluid with a uniformressure thereof .ora uniform temperature. This is accomplishedbyproviding a suitable pressure. regulator 45 .in a conduitcommunicating with'the upper portionvlof the upper tank 40; Thisregulator maybe of any suitable character adapted, whenthe pressure ortemperature exceeds a. predetermined amount, to complete an electric,circuit through conductors 72, 73'and thesolenoid or magnet 74 of thevoltage.regulator,;which may be of anysuitable type, but which isdiagrammatically ;illustrated herein as one adapted-to vary-the numberofprimary coils of the transformer, thereby, in turn,- ;varying thecurrent supplied from the secondaryof the transformer.

In the operation of the device, the electrical current flowing, forexample, from the secondary of the. transformer to the terminal 66,passes through the exterior tubular conductor 54, theheader plate 61,the tubular heatingelements 63, the header plate .62 and the exteriortubular conductor 55 to the terminal 67 and thence to the secondary. Bythis arrangement the current, which desirably is of considerableamperage, but of comparatively low voltage, goes in the oppositedirection in the sections 54 and 55 of theouter conduit to that -inwhich it flows in the corresponding enclosed sections of the tubularheating element, thereby acting to neutralize to a. great extent theeffects of selfinduction, so that the circuit willoperate at a highpower factor.

The fluid desirably is supplied-to the upto the inlet end of the tank49. Thus a coni,

tinuous circulation of the fluid is maintained through the tanks 40 and49, and the liquid vaporized. Thevapors .thereof accumulate in the upperportion of the tank 40 andthe dome 44. andImay -be delivered therefromthrough a suitable outlet ,'pipe or pipes 76 communicating with theupper portion of the drum 40 orits dome 44. i

. The lower. tank 49.desirahly provided with aeblow-ofi77.t-hroi1gh-which; any sediment may beremoved from the lower. tank.:The construction herein described provides an eflicientheater for.liquids having a iyery liighgrate of heat, transfer. and one which can.be constructed 01-1 produced at a low price inany capaeitya,

The heating elements', which are immersed in the. liquid-beinglieated,are of a material not easily affected or corroded by the liquid beingheated and arepractically.indestructi- I ble, therefore requiring o ep ri 1.

Simplified forms-of heating constructions adapted forcpntinuouslyheating a column of liquid areilliistratedin Fig. 9 of the draw- Theconstruction shownin 8 comprises a tubular heating element 78 having awall of relatively high resistance material. such as Monel metal,chtfomenickel steel alloys or other material. having suitable resistanceto corrosionby. thediquid being heated, which is enclosed in aijacketofinsulating material 79. .Theinsulating-jacket'ifi) is surrounded byatubtilar electric ,conductor of low resistance material formed insections 80 and 81, the adjacent ends of which are electricallyconnected, preferably by bands of low resistance metal 82 and 83hai-dngsuitable terminals 84 and 85 to the secondary 86 of atransformer, the primary 87 of which is supplied with analternatingucurrent from a suitable source of electricity; w

The remote ends of the conductor. sections 80 and 81 are electricallyconnected to the heating element 78. In the operation of the device,therefore, the current fiows from the secondary of the transformerthrough the terlittle 01 x1 attention -minal 84 and its band-85, throughthe low resistance conductor section 80. thence through the heatingelement 78. and returns through the low resistance conductor section 81,hand 84 and its terminal 85, to the secondary. By virtue of thisconstruction, the current will flow through the outer low.resistanceconductor sections in the opposite direction from that in which it flowsthrough the sections of the heating element which are enclosed thereby.The effects of self-induction will, therefore, be substantiallyneutralized.

In F ig. 9 another simple embodiment of the invention is illustrated, inwhich a tubular heating element 88 having a wall of Monel metal or otherhigh resistance material is enclosed within and preferably isconcentrically of an exterior conductor formed in sections 89 and 90,the adjacent ends of which are connected to flanges 91 and 92 which areelectrically insulated from each other by a gasket 93 of suitableinsulating material.

I The remote ends of the tubularheating member 88 are mounted insuitable headers 94 and 95 which, for convenience in assembling, arecontained in sleeves 96 and 97 having, respectively, screw-threaded endsfor coupling the same to the conductors 88 and 89 and to the conduitsection 98 and 99 through which fluid is supplied and delivered,respectively. The headers 94 and 95 are identical and are provided withapertures 100 to permit the fluid to flow freely through the headers, sothat the fluid may flow continuously through the space between theheating element 88 and the outer conductor which is formed of thesections 89 and 90. Thus the fluid is heated by direct contact with theinner and outer surfaces of the walls of the heating element 88. Theouter tubular conductor sections v89, 90 may be of low resistancematerial, as aforesaid, or, if greater capacity is required, the outertubular conductor sections 89 and 90 may also be of highresistancematerial, such as Monel metal.

Desirably, the outer tubular conductor sections 89 and 90 are enclosedin a sheathing of insulating material 101, so that radiation of heat tothe atmosphere will be substantial- 1y prevented.

Any suitable means may be employed .for supplying an electric heatingcurrent to the heating element or elements. In the constructiondisclosed herein the headers 91 and 92 are electrically connected to theprimary 102 of a step-down transformer, the primary 103 of which issupplied from a suitable source of electrical energy.

The operation of the construction illus trated in Fig. 9 is in allrespects similar to that described with respect to the constructiondisclosed in Fig.8, with the exception that the column of fluid isdivided into two concentric columns which surround the inner tubularheating element, so that the fluid comes in direct contact with both theinner and outer walls of the inner heating element.

Furthermore, if the exterior tubular conductor sections 89 and 90 arealso of high re sistance material, additional heat will be de livered tothe fluid flowing between the inner heating element and the outerconductor. In this construction, as in the other, the electric currentflows through the exterior conductors 89 and 90 in the oppositedirection to that in which it flows through the corresponding enclosedsections of the inner tubular heating element, so that the effects ofself-induction are substantially neutralized.

It will be observed thattheconstructions disclosed in Figs-8 and 9 areinall respects similar in operation to .the constructions disclosed inboth the other types of apparatus, in that in each case the current iscausedto flow through an exterior tubular conductor in theoppositedirection to that in which it flows through the enclosed heating elementor elements. 3 In all cases, therefore, the arrangement is such as toovercome substantially the eflects of self-induction, Other structionwill be readily obvious upon comparison of the drawings anddescriptions. suitable electric current, eithertdirect or alternating,may be employed. y, Preferably a relatively low tension alternatingcurrent is used and such a currentmay be. supplied from the secondary ofa transformer of any usual type, either, single phase or .polyphase.

It .will be understood that the embodiments of the inventionparticularly disclosed here in are of an illustrative character and arenot restrictive, and variouschanges inform,

construction and arrangement of parts may be made within thespiritandscope of the invention.

. Having thus described the invention, what is claimed as new,,anddesired to be secured by'Letters Patent, s: v

V 1.. A fluid-heating apparatus comprising a tubular heating elementhaving a wall of hlgh resistance material and a low resistanceconductorl for an electric current surrounding said heatinjg element andconnected thereto and arranged in s ul )stant-ially axial parallelismtherewith, means for passingan alternatingelectric current through saidlow resistance conductor and said heating element in opposite directionsthroughout the efl'ective length of said heating element, whereby theeffects of self-induction will be neutralized, and 'means for causingthe fluid .tor flow through said tubular heating element.

2. A fluid-heating apparatus comprising a tubular heating element havinga'wall of relatively high resistance material, a low resistance tubularconductor for an electric current enclosing said heating element andelectrically connected-at one end thereto, means for passing analternating electric current through saidglow resistance conductor andheating element in opposite I direction: throughout the effective lengthof said heat-. ing element, whereby effects of self-induction will beneutralized, and means for causing the fluid to flow through saidtubular low re similarities in consistance conductor and said tubularheating element.

3. A tubular fluid-heating apparatus comprising an outerfluid-containing electric con ductor, a'tubular heating element, havinga wall of high resistance material enclosed within said outer tubularconductor, open at its ends and immersed in said fluid in said outerconductor, means for passing an alternating electric current throughsaid outer conductor'and heating element, whereby heat will betransmitted to the fluid from'both the-inner and outer surfaces ot'thewall of said heating element and means for causing the fluid to flowthrough said outer conduit and said heating element in' the samedirection. 4."A'fluid-heating apparatus comprising an outertubular'fluid-containin' electric conducto'r having a wall of lowresistance mate rial, an inner tubular heating element havin a wall ofrelatively 'high resistance 'materia arrangedfin substantially axialparallelism therewith, means for passing an alternating electric currentthrough said low resistance conductor and heating element in oppositedirections throughout the effective length of said heating element,'toneutralize-the effects of self-induction, and means for causing thefluid to flow both through said conductor and heating element in thesame direction, whereby 'heatwill be transmitted to the flowing fluidfrom both the inner and outer surfaces of the wall of'said heatingelement. f

5. A fluid-heating apparatus comprising an outer tubularfluid-containing electric conductor having a wall of low'resistancemate-- rial, a plurality of tubular heating elements therein havingwallsof relatively high resistance materialarranged in substantiallyaxial parallelism therewith, means for supplying an alternating electriccurrent to said outerconductor, means for causing it to pass throughsaid heating elements in opposite direction to that in'which it assesthrough the outer low resistance con uctor, and means causing the fluidcontained in theouter conductor 'to'flow between and in contact with theouter walls of said tubular heating ele ments in the same direction asthe direction of flow of the fluid within said tubular heating elements.

6; A fluid-heating apparatus comprising an outer tubularfluid-containing conductor having a wall of low resistance material, aplurality of tubular heating elements immersed in said fluid andcommunicating at theirend with said outer conductor and having walls ofrelatively high resistance material arranged in substantial parallelismtherewith, means for causing an electriccurrent to pass through saidconductor'in one direction and through said heating elements in multiplein the opposite directions,,r neans for introducing fluid at one'end ofsaid outer conductor and means for delivering the fluid or itsvaporsfrom the opposite end thereof 7. A fluid-heating apparatus comprising anouter tubular fluid-containing electric conductor'having a wall of lowresistance material, a plurality of tubular heating elements havingwalls of relatively high resistance material arranged in axialparallelism with said outer conductor, insulated therefrom andcommunicating at like ends therewith, a source of electrical energy,means for conducting an electric current therefrom to one end of saidouter conductor,'mcans connecting'the other end of said outer conductorwith the adjacent ends of said tubular heating elements, a returnconductor leading from the opposite endof said heating elements to saidsource of electrical energy, means for introduci-ng'fluid at one end ofsaid outer condu'cto'r, 'a'ndmea'ns for delivering the fluid or itsvapors froni'the other end thereof.

8; A fluid-heating apparatus comprising an'outer tubularfluid-containing electric conductor having 'a wall of low resistancematerial, a plurality of tubular heating elements having walls ofrelatively high resistance material arranged in axial parallelism withsaid outer conductor, insulated therefrom and communicating at likeends-therewith, a source of electrical energy, means for conducting an'el'cctriccurrent therefrom to one end of said outer conductor, meansconnecting the other'end of said outer conductor with the ad jacen'tendsof said tubular heating ele ment's,-a r'e'turn conductor leading fromthe opposite end of said heating elements to said source of electricalenergy, means for introducing fluid at one end of said outer conductor,means for delivering the fluid or its vapors from the outer end thereof,thermostatic means subject to the temperature of the discharging fluid,'and'means operable thereby to regulate the current supplied from saidsource of energy to said heating elements. 9. A fluid-heating apparatuscomprising a cylindrical receptacle having grids extending transverselythereof and insulated therefrom, a plurality of tubular heating elementsmounted in said grids, electrically connected thereto and communicatingat their ends with said receptacle, said receptacle having tubularconducting means of low resistance surrounding said heating elements andelectrically connected at one end to one of said grids, means forcausing an electric current to flow through said low resistance tubularconduct-- ing means and said heating elements in opposite directions,and means for causing the fluid to flow through said heating elements.10. A fluid-heating apparatus comprising a cylindrical receptacle havinggrids extending transversely thereof and insulated therefrom, aplurality of tubular heating elements mounted in said grids,electrically connected thereto and communicating at their ends with saidreceptacle, said receptacle having tuhular conducting means of lowresistance stir rounding said heating elements and electricallyconnected at one end to one of said grids, means for causing an electriccurrent to flow through said low resistance tubular conduct ing meansand said heating elements in opposite directions, means for causing thefluid to flow through said heating elements and a chamber to receive thevapors of said fluid discharged from said heating elements.

11. A fluid-heating apparatus compri ng an outer fluid-containingconductor formed in axially-aligned, connected sections, meanselectrically insulating said sections from each other, a tubular heatingelement within said conductor having a Wall of relatively highresistance material arranged in substantially axial parallelism withsaid outer conductor, insulated therefrom and communicating at its endstherewith, a source of electrical en ergy, conductors leading therefromto the adjacent ends of said outer tubular conductor sections, meansconnecting the remotecnds of said secti ns to the respective adjacentends of said he ting element, means for introducing fluid at one end ofsaid outer tubular conductor, and means for deliver-i the fluid or itsvapor from the other end thereof.

12. A fluid-heating apparatus comprising an outer fluid-containingconductor formed in axially-aligned, connected sections, meanselectrically insulating said sections from each other, a tubular heatingelement within said conductor having a wall of relatively highresistance material arranged in substant ally axial parallelism withsaid outer conductor, insulated therefrom and communicating at its endstherewith, a source of electrical energy, conductors leading therefromto the adjacent ends of said outer tubular conductor sections, meansconnecting the remote ends of said sections to the respective adjacentends of said heating element, means for introducing fluid at one end ofsaid outer tubular conductor, means for delivering the fluid or itsvapors from the other end thereof, and means operable by the conditionof the fluid or its vapors for controlling the cur rent supplied to saidheating element.

13. A fluid-heating apparatus comprising a cylindrical receptacle havinga wall of low resistance material formed in axially-aligned connectedsections providing an outer tubular electric conductor, meanselectrically insulating said sections from each other, a plurality oftubular heating elements having walls of relatively high resistancematerial within said outer conductor arranged in substantially axialparallelism with said outer conductor, insulated therefrom andcommunicating at their ends therewith, a source of electrical energy,conductors leading therefrom to the adjacent ends of said outer tubu-Iar conductor sections, means connecting the remote ends of saidsectionsto the respective adjacentends of said heating elements, meansfor introducing the fluid at one end of said tubular fluid-containingreceptacle and means for delivering the fluid or its vapors from theother end thereof.

14. A fluid-heating apparatus comprising a cylindrical receptacle havinga Wall of low resistance material formed in axially-aligned connectedsections providing an outer tubular electric conductor, meanselectrically insulating said sections from each other, a plurality oftubular heating elements having walls of relativelyhigh resistancematerial within said outer conductor arranged-insubst-antially axialparallelism with said outer conductor, insulated therefrom andcommunicating at their ends therewith, a source of electrical energy,conductors leading therefrom to the adjacent ends of said outer tubularconductor sections, means connectingthe remote ends of said sections tothe respective adjacent ends of said heating elements, means forintroducing the fluid at one end of said fluid-containing receptacle,means for delivering the fluid or its vapors from the other end thereof,and means for circulating the fluid through and around said heatingelements.

15. A fluid-heating apparatus comprising a fluid-containing receptaclehaving an inlet and an outlet and comprising a cylindrical wall of lowresistance material, a plurality of tubular heating elements havingwalls of relatively high resistance material arranged in:

substantially axial alignment with said cylindrical wall, extending aportion of the length of said receptacle and immersed in the fluidtherein, supporting grids for the ends of said tubular heating membersextending itransversely of said tubular conductor, means for passing anelectric current of relatively low potential and high amperage throughsaid cylindrical wall of low resistance and through said heatingelements in opposite directions, whereby the effects of self-inductionwill be substantially neutralized, and means for causing; thecirculation of the fluid through and around said heating elements,whereby heat will be transmitted to the fluid from the inner and outerwalls thereof by direct contact therewith.

16. A fluid heating apparatus comprising a fluid-containing receptaclehaving an in let and an outlet and comprising a cylindrical wall of lowresistance material, a plurality of tubular heating elements havingwalls of relatively high resistance material arranged in substantiallyaxial alignment with said cylindrical wall, extending a portion of thelength of said receptacle and immersed in the fluid therein, supportinggrids for the ends of said tubular heating members extendingtransversely of said receptacle, means for passing an electric currentof relatively low potential and high amperage through said cylindricalwall of low resistance and through said heating elements in-oppositedirections, whereby the effects of self-induc- 5 tion will besubstantially neutralized, means for causing the circulation of thefluid through and around said heating elements, whereby heat will betransmitted to the fluid from the inner and outer walls thereof by di-10 rect contact therewith, and means subject to theinfluence-of thecondition of the fluid within said receptacle to control the currentsupplied to the heating elements.

'In testimony whereof, I hate signed my '15 name to this specification.-

ROBERT A. CARLETONQ

